drivers/ps3: Fix ps3-vuart null dereference

On the unlikely event that drv is null, the current code will
perform a null pointer dereference with it when printing a dev_dbg
message.  Instead, the BUG_ON check on drv should be performed
before we emit the dev_dbg message.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Geoff Levand <geoff@infradead.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

drivers/ps3/ps3-vuart.c

@@ -1000,12 +1000,11 @@ static int ps3_vuart_probe(struct ps3_system_bus_device *dev)
 	dev_dbg(&dev->core, "%s:%d\n", __func__, __LINE__);
 
 	drv = ps3_system_bus_dev_to_vuart_drv(dev);
+	BUG_ON(!drv);
 
 	dev_dbg(&dev->core, "%s:%d: (%s)\n", __func__, __LINE__,
 		drv->core.core.name);
 
-	BUG_ON(!drv);
-
 	if (dev->port_number >= PORT_COUNT) {
 		BUG();
 		return -EINVAL;